Some stator cores are configured such that coils are mounted or fitted on teeth parts of the stator core. The circularity of the stator core (stator-core circularity) and the parallelism of end faces (end-face parallelism) of the stator core are determined depending on press accuracy. For a one-piece stator core which can be produced by a single press work to steel plates, therefore, the stator-core circularity and the end-face parallelism can be easily enhanced as compared with a split stator core produced by assembling split core pieces individually.
The one-piece stator core is manufactured for example by mounting edgewise coils on teeth parts in sequence. However, for a stator core 100, as shown in FIG. 14, when a last coil 109 is to be mounted on a teeth part 108, the last coil 109 interferes with a firstly mounted coil 105 and a coil 107 which are to be adjacent to the coil 109. Specifically, as illustrated in FIG. 15 showing an enlarged view of a part indicated by a chain line R in FIG. 14, the mounting width S of the coil 109 is wider than the mountable width U between the adjacent coils 105 and 107. Thus, the last coil 109 could not be mounted on the teeth part 108. In the case where the coils are mounted on the teeth parts in sequence, therefore, the last coil 109 could not be mounted on the teeth part 108.
As this type of technique, there is conventionally a stator core 200 described in Patent Document 1 shown in FIG. 16. As shown in FIG. 16, stator parts 201 of the stator core 200 are formed, on an inner peripheral, with teeth parts 203. Slits 206 are formed on both sides of each stator part 201. When bundled coil wires are to be mounted on the teeth parts 203 of the stator parts 201, the outer periphery of each stator part 201 is pressed. This causes deformation of each stator part 201 allowed by the slits 206 formed on both sides of each stator part 201. When one stator part 201 is externally pressed, thereby widening the slits 206, the corresponding teeth part 203 is made to protrude inward. Since each teeth part 203 is caused to protrude inward, the bundled coil wires are allowed to be mounted thereon.
As above, the stator parts 201 are pressed externally in sequence so that the bundled coil wires are mounted on the teeth parts 203.